Meniscus Lenses is a curved moon lens consisting of two spherical surfaces with a small radius of curvature and a small numerical difference. It is convex on one side and concave on the other, and it can be either a converging or diverging lens, determined by the refractive index, curvature and radius together.

Positively curved meniscus lenses are designed to minimize spherical aberration and can be used alone for minimum convergence spot, or when used in combination with other lenses to shorten the focal length and thus increase the numerical aperture.

Negatively curved moon lenses have a thinner center section than the edges, which causes light to diverge and is intended to minimize spherical aberration. They are often used in conjunction with other lenses to increase the focal length and thus reduce the numerical aperture (NA) of the optical system.